The present invention relates to a lamp holder having two terminals arranged at the end of two wires of a light string and a light bulb preassembled in a lamp base. Electrodes from the lamp and base make contact with the terminals as the lamp is inserted into the inside of the lamp holder. A bulge is arranged at on position within the lamp base. An electrically conductive spring is arranged in the inside of the lamp holder having two feet corresponding to the positions of the terminals. Each foot is in contact with one of the terminals when the bulb and base are out of the holder, but one foot is displaced by the bulge on the lamp base to provide electrical connection through the lamp rather than the spring when the lamp is inserted into the holder.